JP3824584B2 - Method and apparatus for controlling packet data transmission between base station controller and base station - Google Patents

Description

  The present invention relates to packet data transmission in a mobile communication network, and more particularly to a method and apparatus for controlling packet data transmission between a base station controller and a base station.

  Generally, such as CDMA (Code Division Multiple Access) 2000, WCDMA / UMTS (Wideband Code Division Multiple Access / Universal Mobile Telecommunications System), GPRS (General Packet Radio System) and CDMA2000 1xEV-DO (Evolution-Data-Only). A mobile communication network includes a base station controller (BSC) and a base station (Base Transceiver System: BTS). Such a mobile communication network has a form in which only a voice service is provided to a mobile subscriber. However, the mobile communication network tends to be developed to support not only a voice service but also a packet data service.

FIG. 1 is a diagram illustrating a configuration of a general mobile communication network that supports not only voice services but also packet data services to mobile subscribers.
Referring to FIG. 1, a mobile communication network includes mobile terminals (Mobile Station: MS) 11 and 12, which are users, base stations (BTSs) 20 and 30, which are wirelessly connected to the mobile terminals and communicate with each other. A base station controller (BSC) 40 that is connected to the base stations 20 and 30 by wire and communicates by wire is included. The base station controller 40 is connected to a mobile switching center (MSC) 50 and a gateway (GW) 60. The mobile switch 50 is connected to a public switching telephone network (PSTN), and the gateway 60 is connected to the Internet / public packet data network (PSDN). Therefore, when the mobile terminal 11 is connected to the PSTN through the mobile switch 50 under the control of the base station controller 40, the mobile terminal 11 is provided with a voice service. When the mobile terminal 11 is connected to the Internet / PSDN through the gateway 60, a packet data service is provided to the mobile terminal 11.

  The base stations 20 and 30 include radio frequency schedulers 21 and 31, respectively. The base station controller 40 includes a selection and distribution unit (SDU) / radio link protocol (RLP) unit 41. The RF schedulers 21 and 31 are provided to support the base stations 20 and 30 to efficiently use radio resources and to appropriately use a limited radio resource by a plurality of users. . The SDU is provided for transmitting traffic to a plurality of base stations and combining data of the same mobile terminal received from the plurality of base stations. The SDU may be included in the gateway 60 to perform the same function. However, here, the SDU is included in the base station controller 40. The RLP changes packet data traffic received from the gateway 60 to an error control protocol frame structure and transmits the packet data traffic to the base stations 20 and 30. Here, the base stations 20 and 30 should have a buffer space of a limited size for users. Therefore, if traffic exceeding the amount that can be allocated to the user corresponding to the base stations 20 and 30 is received from the base station controller 40, traffic loss is inevitably generated in the base stations 20 and 30. To do. For traffic lost in communication between the base stations 20 and 30 and the base station controller 40, error control between the mobile terminal (for example, the mobile terminal 11) and the base station controller 40 ( For example, the retransmission procedure is performed through an error recovery (RLP) function. The retransmission procedure causes a delay and a decrease in radio resource efficiency. Further, the mobile terminal can perform handoff during movement between a plurality of base stations. Therefore, if excessive traffic is transmitted to the base station, a situation may occur in which the mobile terminal must discard the traffic during handoff, and consequently, to transmit the traffic, The efficiency of the link used between the base station controller and the base station is reduced.

  The packet data transmission control operation between the base station controller and the base station according to the prior art for solving such problems is shown in FIGS. In the following description, it is assumed that the packet data transmission control operation is performed between the base station controller 40 and the base station 20 of FIG. The term “BSC_BUF” indicates the amount of packet data traffic stored in the internal buffer of the base station controller 40 (hereinafter referred to as buffer storage amount), and “BTS_BUF” is stored in the internal buffer of the base station 20. The amount of packet data traffic stored (hereinafter referred to as buffer storage amount) is indicated, and “BTS_Q_SIZE” indicates the maximum amount of packet data traffic that can be stored in the internal buffer of the base station 20. That is, “BSC_BUF” indicates the current size of the internal buffer of the base station controller 40, “BTS_BUF” indicates the current size of the internal buffer of the base station 20, and “BTS_Q_SIZE” indicates the base station The maximum size of 20 internal buffers is shown.

FIG. 2 is a diagram illustrating a procedure of packet data transmission control in a base station controller according to the prior art.
Referring to FIG. 2, the base station controller 40 waits for packet data traffic from the gateway 60 or a buffer storage amount to be reported from the base station 20 (S201). When the buffer storage amount is reported from the base station 20, the base station controller 40 updates the reported buffer storage amount to the current buffer size BTS_BUF of the base station 20 (step S209).

  When packet data traffic is received from the gateway 60, the base station controller 40 stores the received traffic in an internal buffer (S203), and receives the size BSC_BUF of the current buffer of the base station controller. The traffic is increased by the amount of traffic (step S204). If the current buffer size BTS_BUF of the base station 20 is smaller than the maximum buffer size BTS_Q_SIZE allocated to the corresponding user by the base station 20 (“Yes” in step S205), the base station controller 40 The traffic stored in the buffer is transmitted to the base station 20 as much traffic as the base station 20 can accommodate, that is, (BTS_Q_SIZE−BTS_BUF) (step S206). After transmitting the traffic to the base station 20, the base station controller 40 decreases the size BSC_BUF of the current buffer of the base station controller by the amount of the transmitted traffic (S207).

  If BTS_BUF is the same as BTS_Q_SIZE, it means that the amount of traffic that can be transmitted reaches a limit value (“No” in step S205), so that the base station controller 40 determines that BTS_BUF decreases to BTS_Q_SIZE or less. Wait (step S201). When it is reported from the base station 20 that BTS_BUF is smaller than BTS_Q_SIZE, the base station controller 40, among the traffic stored in the internal buffer, transmits the traffic that can be accommodated by the base station 20 to the base station. 20 (step S206).

FIG. 3 is a diagram illustrating a transmission procedure of a control message having current buffer size information in a base station according to a conventional technique.
Referring to FIG. 3, the base station 20 of FIG. 1 waits for a control message transmission time (step S301). When the control message transmission time is reached (“Yes” in step S302), the base station 20 transmits a control message including BTS_BUF and BTS_Q_SIZE, which are size information of the BTS current buffer, to the base station controller 40 (step S303). . Here, the “control message transmission time” may be set to a preset period or a time during which traffic is transmitted to the base station controller 40. When traffic is transmitted to the base station controller 40, BTS current buffer size information BTS_BUF is transmitted as in-band information of the opposite traffic.

FIG. 4 is a diagram illustrating a packet data transmission operation between a base station controller and a base station according to a conventional technique. Here, it is assumed that BTS_Q_SIZE is 64 packets and that BTS_BUF is initially free.
Referring to FIG. 4, when it is assumed that 64 packets are received from the gateway 60 to the base station controller 40 (step 40a), the base station controller 40 stores the received packets in an internal buffer. , BSC_BUF is increased to 64. The base station controller 40 determines that 64 packets can be transmitted because the number of packets currently stored (overlapped) in the base station 20 is 0, and the 64 packets are transmitted. Transmit to the base station 20 (step 40b). The 64 packets transmitted by the base station controller 40 are received by the base station 20 (step 40c). After receiving the 64 packets, the base station 20 reports that the current buffer size of the base station has increased to 64 packets by transmitting a control message at a preset control message transmission time. (Step 40d). When the control message is received from the base station 20, the base station controller 40 sets the current buffer size BTS_BUF of the base station to 64 packets. At this time, since the current buffer size BTS_BUF of the base station is the same as the maximum buffer size BTS_Q_SIZE of the base station, the base station controller 40 recognizes that further packet transmission is impossible.

In this situation, when 64 new packets are received, the base station controller 40 stores the 64 new packets in an internal buffer and updates the current buffer size BSC_BUF of the base station controller (40e). Stage). At this time, since the size of the current buffer of the base station is 64 packets, which is the size of the maximum buffer of the base station, the base station controller 40 stands by without transmitting the 64 new packets.
Next, the base station 20 transmits 32 packets to the mobile terminal 11 (step 40f) and reports to the base station controller 40 that the current buffer size of the base station is 32 packets (step 40g). . Then, the base station controller 40 determines that the amount of packets that can be transmitted to the base station 20 has increased to 32 packets, and based on the determination, 32 of the 64 packets stored in the internal buffer. Packets are transmitted to the base station 20.

  The packet data transmission operation of FIG. 4 will be described with respect to a case where the base station controller 40 and the base station 20 are in a normal state. However, the base station controller 40 and the base station 20 may not be in a normal state. For example, when a packet transmitted from the base station controller 40 arrives at the base station 20 after a relatively large delay due to link delay or buffering between the base station controller and the base station. May occur. An example of packet data transmission operation between the base station controller and the base station in such a case is shown in FIG.

FIG. 5 shows another procedure of packet data transmission operation between the base station controller and the base station according to the prior art. Here, it is assumed that BTS_Q_SIZE is 64 packets and that BTS_BUF is initially free.
Referring to FIG. 5, when it is assumed that 64 packets are received from the gateway 60 to the base station controller 40 (step 50a), the base station controller 40 stores the received packets in an internal buffer. , BSC_BUF is increased to 64. At this time, since the base station controller 40 can transmit 64 (= BTS_Q_SIZE [64] −BTS_BUF [0]) packets, it transmits 64 packets to the base station 20 (step 50b). ).

  In some cases, the base station controller 40 receives 64 new packets before the transmitted 64 packets arrive at the base station 20, otherwise BTS_BUF is updated in the BSC. (Step 50c). When receiving a new packet, the base station controller 40 calculates the usable reception amount of the base station 20. In this case, since the transmitted 64 packets have not yet arrived at the base station 20 and the BTS_BUF of the BSC still indicates 0, the base station controller 40 erroneously determines that the BTS_BUF is 0. To do. Therefore, the base station controller 40 calculates the amount of traffic that the base station 20 can additionally receive to 64 (= BTS_Q_SIZE [64] −BTS_BUF [0]) packets, and receives 64 new packets received. Is transmitted to the base station 20 (step 50d).

  Accordingly, the base station 20 receives the 64 packets transmitted in the step 50b and additionally receives the 64 packets transmitted in the step 50d. In this case, the amount of packets received by the base station 20 exceeds the maximum size that can be stored in the internal buffer of the base station 20, that is, the limit value of 64 packets. This causes an overflow of the internal buffer of the base station 20, and re-transmission occurs between the mobile terminal 11 and the base station controller 40 (more specifically, SDU / RLP 41). As a result, the efficiency of radio resources is reduced, and a delay due to retransmission occurs. In particular, such a problem becomes serious when traffic is transmitted to a base station in a handover situation of a mobile communication network.

Accordingly, an object of the present invention is to provide a method and apparatus for controlling packet data transmission between a base station controller and a base station of a mobile communication network.
It is another object of the present invention to provide a method and apparatus for removing an overflow generated in a base station internal buffer during packet data transmission between a base station controller and a base station of a mobile communication network.

It is another object of the present invention to provide a method and apparatus for preventing a reduction in the efficiency of radio resources due to retransmission of packet data from a base station controller of a mobile communication network to a base station.
It is another object of the present invention to provide a method and apparatus for removing delay caused by retransmission of packet data during packet data transmission between a base station controller and a base station of a mobile communication network.
It is another object of the present invention to provide a method and apparatus for accurately determining the number of packet data transmitted from a base station controller of a mobile communication network to a base station.

In order to achieve such an object, in order to transmit packet data to a mobile terminal, the present invention receives packet data from the base station controller and stores the packet data in a base station having a buffer for temporarily storing the packet data. A method and apparatus for controlling to transmit as much packet data as can be stored in the buffer during transmission is proposed.
According to a first aspect of the present invention, a base station controller that receives packet data, and a base station that includes a buffer that receives and stores packet data for transmission to a mobile terminal from the base station controller. In a method for controlling packet data transmission to the base station by the base station controller in a mobile communication network including: when packet data is received, the size of the buffer of the base station, and from the base station controller The process of comparing the number of packet data transmitted to the base station but not yet transmitted from the base station to the mobile terminal, and the buffer size of the base station is not transmitted to the mobile terminal And transmitting the received packet data to the base station if the number is larger than the number of packet data.

  According to a second aspect of the present invention, mobile communication includes a base station controller that receives packet data and a base station that includes a buffer that receives and stores packet data for transmission to a mobile terminal from the base station controller. In a method for controlling packet data transmission between the base station controller and the base station in a network, packet data transmitted from the base station controller to the mobile terminal after being received by the base station. The number is transmitted from the base station controller to the base station based on the process of reporting the number to the base station controller and the reported number of packet data. The process of calculating the number of packet data not yet transmitted, and when the packet data is received, the base station controller determines the size of the buffer and the transmitted data. Comparing the number of unacknowledged packet data, and transmitting the received packet data from the base station controller to the base station when the size of the buffer is larger than the number of untransmitted packet data. Including.

  According to a third aspect of the present invention, mobile communication including a base station having a base station controller that receives packet data and a buffer that receives and stores packet data for transmission to a mobile terminal from the base station controller. In a method for calculating the number of packet data transmitted from the base station controller to the base station in a network, a first number indicating the number of packet data transmitted from the base station to the mobile terminal and the buffer A process of reporting a second number indicating the number of stored packet data to the base station controller by the base station, and when the first number and the second number are 0, from the base station controller A third number indicating the number of packet data that has been transmitted to the base station at a previous reporting time but has not yet been transmitted from the base station to the mobile terminal, and the base at the current reporting time A step of checking whether a fourth number indicating the number of packet data transmitted from the station controller to the base station but not transmitted from the base station to the mobile terminal is the same; A step of setting the number of packet data transmitted from the base station controller to the base station to 0 when the third number and the fourth number are the same.

  As described above, a base station controller according to an embodiment of the present invention can deliver an amount of traffic that exactly matches the size of the base station buffer. Therefore, by preventing overflow of the base station buffer, the number of retransmissions between the base station controller and the mobile terminal is reduced. The reduction in the number of retransmissions has the advantage of increasing the efficiency of radio resources. Particularly, it is possible to prevent the link efficiency between the base station controller and the base station from being lowered due to traffic transmission to the base station which is unnecessary in the handover situation of the mobile communication network.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments according to the invention will be described in detail with reference to the accompanying drawings. In the following description, for the purpose of clarifying only the gist of the present invention, a specific description relating to related known functions or configurations is omitted.
In the following description, the packet data transmission operation according to the embodiment of the present invention is applied to the mobile communication network of FIG. Embodiments of the present invention can also be applied to IS-95A / B, GSM (Global System for Mobile communication), IS-2000, WCDMA, UMTS, CDMA2000 1xEV-DO, and GPRS. The packet data transmission operation according to the embodiment of the present invention is performed by a base station controller (specifically, SDU) and a base station of the mobile communication network.

FIG. 6 is a diagram showing a detailed configuration of the base station controller 40 shown in FIG. 1 to which the present invention is applied.
Referring to FIG. 6, the base station controller 40 includes a main controller 410, a line interface 420, a switch (intra-BSC switch (or router) 430), a line interface (line interface). Line Interface) 440 and SDU / RLP processor 41.

  The main controller 410 generally controls the operation of the base station controller 40. The line interface 420 is provided for connection with a gateway (GW) 60, and the line interface 440 is provided for connection with the base station 20. The switch 430 routes traffic in the base station controller 40. The SDU (Selection & Distribution Unit) processor 41 multiplexes / demultiplexes traffic transmitted / received through two or more links at the time of soft handover. The RLP (Radio Link Protocol) processor 41 supports error recovery of a radio link.

The packet data transmission control operation proposed by the present invention can be implemented with a physically separate device, but here it is implemented in software in the SDU / RLP processor (Processor) 41. Assume that. The software implementation makes it possible to use a module in an existing base station controller as it is.
The SDU / RLP processor 41 manages a record as shown in FIG. 9 for each user for operation according to an embodiment of the present invention.

Referring to FIG. 9, the user record includes User-ID, NUM _{TX_SDU2BTS} , NUM _{TX_BTS2AIR} , and Q _{BTS_Q_PER_USER} . User-ID is a key of a record for identifying each user. The NUM _{TX_SDU2BTS} is the number of _packets that the base station controller 40 (specifically, the SDU 41) transmits to the base station 20, but the base station 20 is still wireless, that is, the number of packets that have not been transmitted to the mobile terminal. Indicates. NUM _{TX_BTS2AIR} indicates the number of packets transmitted from the base station 20 to the mobile terminal 11 through the radio link. Q _{BTS_Q_PER_USER} indicates a limit value of a buffer allocated to a corresponding user in the base station 20, that is, a size of an internal buffer provided for transmission to the mobile terminal 11. The Q _{BTS_Q_PER_USER} is a value recognized by the base station controller 40 in advance, and the NUM _{TX_BTS2AIR} is a value reported at a control message transmission time preset by the base station 20.

FIG. 7 is a diagram showing a detailed configuration of the base station shown in FIG. 1 to which the present invention is applied. Here, it is assumed that the base station is the base station 20 of FIG. 1, but the other base stations 30 have the same configuration.
Referring to FIG. 7, the base station 20 includes a main controller 210, a line interface 220, a switch (or intra-BTS switch) (or router) 230, a channel card (Channel). Cards) 241 to 243, a radio frequency (RF) transmitter / receiver 250, and an RF scheduler 21.

  The main controller 210 generally controls the operation of the base station 20. The line interface 220 is provided for connection with the base station controller 40. The RF transceiver 250 is provided for transmitting and receiving data and control signals to and from a mobile station (MS) 11. The switch 230 determines a traffic route in the base station. The RF scheduler 21 supports efficient management of radio resources. The RF scheduler 21 can be implemented as a separate independent processor, or can be implemented as software in the channel cards 241 to 243.

Although the packet data transmission control operation proposed by the present invention can be implemented physically through a separate device, it is assumed here that the packet data transmission control operation is implemented in software in the channel cards 241 to 243. This software implementation makes it possible to use a module in an existing base station as it is.
FIG. 8 is a diagram showing a detailed configuration of the channel card shown in FIG. Here, it is assumed that the channel card is the channel card 241, but the other channel cards 242 to 243 have the same configuration.

Referring to FIG. 8, the channel card 241 includes an input / output interface 24-1, a main processor 24-2, a memory 24-3, and a modulator 24. -4 and a demodulator 24-5.
The input / output interface 24-1 is provided for connection with the switch 230. The modulator 24-4 modulates data and control signals transmitted to the mobile terminal 11 through the RF transmitter 251. The demodulator 24-5 demodulates data and control signals received from the mobile terminal 11 through the RF receiver 252. The memory 24-3 includes an internal buffer that receives packet data transmitted to the mobile terminal 11 from the base station controller 40 and buffers (temporarily stores) the data. Further, the memory 24-3 can store various control information. The main processor 24-2 controls a packet data transmission operation according to an embodiment of the present invention. The main processor 24-2 can have the function of the RF scheduler 21 shown in FIG.

FIG. 10 shows a procedure of packet data transmission control in the base station controller according to the embodiment of the present invention. The packet data transmission control procedure is performed by the SDU processor 41 of the base station controller (BSC) 40 shown in FIG. 6, but will be described assuming that it is performed by the BSC 40 for convenience of explanation.
Referring to FIG. 10, in step 1001, the BSC 40 waits for reception of packet data traffic from the gateway (GW) 60 or reception of a control message from the base station (BTS) 20. If it is determined in step 1002 that packet data traffic (hereinafter referred to as a packet) has been received from the gateway 60, the BSC 40 stores the received packet in an internal buffer in step 1003. Next, in step 1004, the _{BSC 40} calculates the number of usable packets that can be transmitted to the BTS 20 using the value of Q _{BTS_Q_PER_USER and} the value of NUM _{TX_SDU2BTS} . _If the value of Q _{BTS_Q_PER_USER} is larger than the value of NUM _{TX_SDU2BTS} in step 1004, the _BSC 40 transmits a packet having a value of Q _{BTS_Q_PER_USER-} NUM _{TX_SDU2BTS to} the BTS 20 in step 1005. The value of Q _{BTS_Q_PER_USER is} a value indicating the size of the internal buffer of the BTS 20. The value of NUM _{TX_SDU2BTS} indicates the number of packets that the BSC 40 has transmitted to the BTS 20, but the BTS 20 has not yet transmitted wirelessly to the mobile terminal, and is a control message reported (transmitted) from the BTS 20. It is an included value. After transmitting the packet to the BTS 20, the BSC _{40 increases} the value of NUM _{TX_SDU2BTS} by the number of packets transmitted to the BTS in step 1006. That is, NUM _{TX_SDU2BTS} indicates the number of packets transmitted to the BTS 20 by the BSC 40.

If it is determined in step 1007 that a control message has been received from the BTS 20, the BSC 40 is transmitted to the mobile terminal 11 through the radio link by the BTS 20 included in the received control message in step 1008. Information on the number of packets is obtained, and NUM _{TX_BTS2AIR} is updated to the obtained value in step 1009. In step 1010, the BSC40 calculates _{NUM TX_SDU2BTS} by using the updated _{NUM TX_BTS2AIR.} This calculation is performed by updating NUM _{TX_SDU2BTS} to (NUM _{TX_SDU2BTS−} NUM _{TX_BTS2AIR} ). That is, in step 1010, the BSC 40 is currently stored in the BTS 20 by calculating the remaining packets excluding the packets transmitted to the mobile terminal 11 through the wireless link among the packets transmitted to the BTS 20. Calculate the number of packets. After performing step 1010, the BSC 40 determines in step 1011 whether the internal buffer of the BSC 40 is free. If the BSC internal buffer is not empty, it means that there are still packets to be transmitted to the BTS 20. In this case, the BSC 40 proceeds to step 1004 to determine the number of usable packets that can be transmitted to the BTS 20, and in step 1005, the BSC 40 transmits as many packets as the number of usable packets. _Since the value of NUM _{TX_BTS2AIR is} a value that is temporarily used, in the actual implementation, one field value of a control message transmitted from the BTS 20 to the BSC 40 can be used without defining the variable NUM _{TX_BTS2AIR} . .

  FIG. 11 is a diagram illustrating a control message transmission procedure including information on the number of transmitted packets in a base station (BTS) according to an embodiment of the present invention. In this embodiment, the transmission procedure of the control message is performed by the main processor 24-2 of the channel card of the base station (BTS) 20 shown in FIG. 7 and FIG. The explanation will be made assuming that it will be carried out.

  Referring to FIG. 11, the BTS 20 waits for a control message transmission time in step 1101. If it is determined in step 1102 that it is the control message transmission time, the BTS 20 transmits a control message including information on the number of packets transmitted to the mobile terminal 11 through a wireless link to the BSC 40 in step 1103. . Here, the “control message transmission time” may be set to a preset period, or may be set to a time for the BTS 20 to transmit traffic through a radio link. When the control message is transmitted periodically, the BTS 20 reports to the BSC 40 the number of packets transmitted through the radio link during the period unit time. However, when the control message is reported when traffic is transmitted through a radio link, the BTS 20 reports the number of packets transmitted at the corresponding time to the BSC 40.

FIG. 12 is a diagram illustrating an example of a packet data transmission operation between the base station controller (BSC) 40 and the base station (BTS) 20 according to the embodiment of the present invention. Here, it is _{assumed that} the value of Q _{BTS_Q_PER_USER} indicating the size of the internal buffer of the BTS 20 is 64 packets, and that no packet is initially transmitted from the BSC 40 to the BTS 20.
Referring to FIG. 12, when packet data traffic is received from the gateway 60 in step 120a, the BSC 40 calculates the amount of packets that can be transmitted to the BTS 20 (see step 1004 in FIG. 10). In this case, since no packet is transmitted from the BSC 40 to the BTS 20, the BSC 40 determines that 64 (= Q _{BTS_Q_PER_USER−} NUM _{TX_SDU 2} BTS) packets can be transmitted to the BTS 20. Accordingly, in step 120b, the BSC 40 transmits 64 packets to the BTS 20, and updates the NUM _{TX_SDU2BTS} indicating 64 to the number of packets transmitted from the BSC 40 to the BTS 20.

Here, it is assumed that a new 64 packet arrives at the BSC 40 in step 120c before the 64 packets transmitted by the BSC 40 arrive at the BTS 20. In this case, since the 64 packets transmitted by the BSC 40 have not yet arrived at the BTS 20 or have arrived but have not been transmitted to the mobile terminal 11 through the wireless link, the BSC 40 further transmits the packet. It can be recognized that there is no packet that can be transmitted to the BTS 20. This is from Q _{BTS_Q_PER_USER-} NUM _{TX_SDU2BTS} = 64-64 = 0. Here, the BSC 40 stores the 64 newly received packets in an internal buffer. In step 120d, the BTS 20 receives only 64 packets transmitted by the BSC 40 in step 120b. This is because the BSC 40 did not transmit the new 64 packet to the BTS 20 even if a new 64 packet was received in step 120c. The new 64 packets are transmitted from the BSC 40 to the BTS 20 when the BTS 20 transmits the received 64 packets to the mobile terminal 11 through a wireless link and reports the transmission result to the BSC 40.

FIG. 13 is a diagram illustrating another example of packet data transmission operation between the base station controller (BSC) 40 and the base station (BTS) 20 according to the embodiment of the present invention. Here, it is assumed that the value of Q _{BTS_Q_PER_USER} indicating the size of the internal buffer of the BTS 20 is 64 packets, and that no packet is initially transmitted from the BSC 40 to the BTS 20.
Referring to FIG. 13, 48 packets arrive at the BSC 40 in step 130a. When the BSC 40 receives the 48 packets, the BSC 40 calculates the amount of packets that can be transmitted to the BTS 20 (see step 1004 in FIG. 10). At this time, since no packet is transmitted from the BSC 40 to the BTS 20, the BSC 40 determines that 64 (= Q _{BTS_Q_PER_USER−} NUM _{TX_SDU 2} BTS) packets can be transmitted to the BTS 20. Accordingly, in step 130b, the BSC 40 transmits 48 packets to the BTS 20, and updates the NUM _{TX_SDU2BTS} indicating 48 to the BTS 20 from the _{BSC 40} .

Upon receiving the 48 packets, the BTS 20 transmits 36 packets to the mobile terminal 11 through the wireless link in step 130c, and transmits a control message including the number of packets transmitted through the wireless link to the BSC 40 in step 130d. To report the number of transmitted packets.
When the number of transmitted packets is reported, the BSC 40 updates the value of NUM _{TX_BTS2AIR} to 36 in step 130e, and updates the value of NUM _{TX_SDU2BTS} in step _130f . The value of the updated _{NUM TX_SDU2BTS} is calculated by subtracting the value of the updated _{NUM TX_BTS2AIR} from the value of the previous _{NUM TX_SDU2BTS.} That is, the updated NUM _{TX_SDU2BTS} value is calculated by subtracting the updated NUM _{TX_BTS2AIR} value 36 from the previous NUM _{TX_SDU2BTS} value 48. The BSC 40 determines the number of packets that can be transmitted to the BTS 20 using the updated NUM _{TX_SDU2BTS} value and the value of Q _{BTS_Q_PER_USER} indicating the size of the internal buffer of the BTS 20. That is, the BSC 40 determines that 52 (= Q _{BTS_Q_PER_USER-} NUM _{TX_SDU2BTS} = 64-12) packets can be transmitted to the BTS 20. Here, it is assumed that 52 new packets are received from the gateway 60. Accordingly, in step 130g, the BSC 40 transmits 52 packets to the BTS 20, and 64 NUM _{TX_SDU2BTS} indicating the number of packets transmitted from the BSC 40 to the BTS 20 (currently transmitted to the number of previously transmitted packets 12). Updated to the number calculated by adding the number 52 of packets that have been added.

  The BTS 20 does not transmit any packet to the mobile terminal 11 through the radio link in step 130h, and transmits a control message including the number of packets transmitted through the radio link to the BSC 40 in step 130i. Report the number of packets transmitted.

When the number of transmitted packets is reported, the BSC 40 updates the value of NUM _{TX_BTS2AIR} to 0 in step _130j . At this time, the value of the updated _{NUM TX_BTS2AIR} is _0, the operation to update the value of the _{NUM TX_SDU2BTS} is unnecessary. The BSC 40 determines the number of packets that can be transmitted to the BTS 20 using the previously updated NUM _{TX_SDU2BTS} value and the value of Q _{BTS_Q_PER_USER} indicating the size of the internal buffer of the BTS 20. That is, the BSC 40 determines that 0 (= Q _{BTS_Q_PER_USER-} NUM _{TX_SDU2BTS} = 64-64) packets can be transmitted to the BTS 20.

Then, the BTS 20 transmits 36 packets to the mobile terminal 11 through the radio link in step 130k, and transmits a control message including the number of packets transmitted through the radio link to the BSC 40 in step 130l. Report the number of packets received.
When the number of transmitted packets is reported, the BSC 40 updates the value of NUM _{TX_BTS2AIR} to 36 in step _130m , and updates the value of NUM _{TX_SDU2BTS} in step _130n . The value of the updated _{NUM TX_SDU2BTS} is calculated by subtracting the value of the updated _{NUM TX_BTS2AIR} from the value of the previous _{NUM TX_SDU2BTS.} That is, the updated NUM _{TX_SDU2BTS} value becomes 28 by subtracting the updated NUM _{TX_BTS2AIR} value 36 from the previous NUM _{TX_SDU2BTS} value 64. The BSC 40 determines the number of packets that can be transmitted to the BTS 20 using the updated NUM _{TX_SDU2BTS} value and the value of Q _{BTS_Q_PER_USER} indicating the size of the internal buffer of the BTS 20. That is, the BSC 40 determines that 36 (= Q _{BTS_Q_PER_USER-} NUM _{TX_SDU2BTS} = 64-28) packets can be transmitted to the BTS 20. Accordingly, the BSC 40 transmits 36 packets to the BTS 20.

Theoretically, there is no loss in the link between BSC 40 and BTS 20. In practice, however, the possibility of loss occurring in the link cannot be excluded. Cases in which loss occurs in the link are classified into two, each having the following problems.
First, if a packet transmitted by the BSC 40 cannot arrive at the BTS 20 due to a loss of link between the BSC 40 and the BTS 20, the BSC 40 will still send the lost packet to the internal buffer of the BTS 20. There is a problem of misrecognizing that it is buffered. For example, it may be assumed that the BSC 40 has transmitted 64 packets to the BTS 20, but one of the packets has been lost on the link between the BSC 40 and the BTS 20. In this case, the BSC 40 sets NUM _{TX_SDU2BTS} to 64. However, the BTS 20 actually receives only 63 packets, and after transmitting all the 63 packets to the mobile terminal 11, reports to the BSC 40 that the 63 packets have been transmitted. . Therefore, NUM _{TX_SDU2BTS} is updated to 1 (= 64-63). Although there are no more packets to be transmitted in the BTS 20, the BSC 40 continuously maintains NUM _{TX_SDU2BTS} at 1, so the BSC 40 erroneously determines that there is one packet to be transmitted through the BTS 20. As a result, the number of usable packets that can be transmitted from the BSC 40 to the BTS 20 is reduced.

Second, control messages reported to the BSC 40 by the BTS 20 are lost during transmission. In this case, the BTS 20 has transmitted a control message in advance, but the BSC 40 cannot receive a report indicating control message transmission. The BSC 40 erroneously recognizes that a packet transmitted to the internal buffer of the BTS 20 is stored.
Furthermore, the present invention proposes a method for solving the problems caused by the loss occurring in the link between the BSC 40 and the BTS 20. In order to solve the above problems, the STS 41 of the BTS 20 and the BSC 40 performs the following functions.

The BTS 20 not only reports the number of packets transmitted to the mobile terminal 11 through a radio link to the BSC 40, but also reports the number of packets buffered in the buffer of the BTS 20 to the BSC 40. These reports may be performed periodically through the control message, as described above, or may be performed when the BTS 20 transmits a packet to the mobile terminal 11.
SDU41 of the BSC40 the variable _{Q BTS_Q_PER_USER} described above, _{NUM TX_SDU2BTS,} and besides _{NUM TX_BTS2AIR,} manages _OLD-NUM TX_SDU2BTS, NUMreset, and variables MAXreset. _Here, the value of _{OLD-NUM TX_SDU2BTS} indicates the value of the _{NUM TX_SDU2BTS} at which previous reports from the BTS20 is received. Other variables NUMreset and MAXreset will be described later.

FIG. 14 is a diagram showing a procedure of packet data transmission control in the base station controller (BSC) 40 according to another embodiment of the present invention. This procedure accurately determines the number of packet data transmitted from the BSC 40 to the BTS 20.
Referring to FIG. 14, if it is determined in step 1401 that a control message has been received from the BTS 20, the BSC 40 analyzes a field of the received control message in step 1402. As a result of the analysis, if the number of packets transmitted to the mobile terminal 11 through the radio link by the BTS 20 is 0 and the size of the buffer of the BTS 20 is also 0, the BSC 40 determines in step 1403 the current reporting time point. the value of the _{NUM TX_SDU2BTS} checks whether the same as the value of _{OLD-NUM TX_SDU2BTS} in previously reported point in. If the values are the same from the inspection results, the BSC 40 increments NUMreset by 1 in step 1404, and determines in step 1405 whether the value of NUMreset is the same as the value of MAXreset. If the NUMreset value is the same as the MAXreset value, that is, if the NUMreset value is the same as a preset value, the BSC 40 sets the _{NUMTX_SDU2BTS} value to 0 in step 1406. To do. However, if the value of the NUMreset is not the same as the value of the MAXreset, the BSC 40 returns to step 1401. The value of the MAXreset can be set to a value suitable for the operator of the mobile communication network.

In the procedure of FIG. 14, the buffer state of the BTS 20 determined by the BSC 40 and the internal state value reported by the BTS 20 during a period in which no user packet is generated and no packet to be transmitted to the BTS 20 exists. Are not identical, the corresponding state value of the _{BSC 40} (ie, NUM _{TX_SDU2BTS} ) is initialized to zero. By such an operation, even if a link loss occurs between the BSC 40 and the BTS 20, the procedure according to the embodiment of the present invention shown in FIG. 10 can be accurately performed.

  FIGS. 15A and 15B are diagrams showing simulation results for judging the performance of the size of the base station buffer when the packet data transmission operation according to the conventional technique and the embodiment of the present invention is applied, respectively. It is. The simulation results assume that a 200 ms delay occurs during packet transmission between the BSC and the BTS, and that the buffer limit value (maximum size) for storing user packets is 30 packets. Carried out. The assumed packet data traffic pattern is one web (World Wide Web: WWW) user.

FIG. 15A shows the size of the BTS buffer when the conventional packet data transmission operation is applied, and FIG. 15B shows the case where the packet data transmission operation according to the embodiment of the present invention is applied. Indicates the size of the BTS buffer. In FIG. 15, the x-axis is the simulation time, and the y-axis is the BTS buffer size.
Referring to FIG. 15A, it can be seen that although the maximum limit value is set to 30 packets, a maximum of about 140 packets are provided to the BTS. Therefore, a maximum of 110 packets may be discarded due to overflow of the BTS buffer.

However, referring to FIG. 15B, it can be seen that the number of packets provided to the BTS never exceeds the maximum limit of 30 packets. That is, no overflow occurs in the BTS buffer.
As described above, the detailed description of the present invention has been described in detail with reference to specific embodiments. However, the scope of the present invention should not be limited by the above-described embodiments, and various modifications can be made within the scope of the present invention. It will be apparent to those skilled in the art that variations are possible.

It is a figure which shows the structure of a general mobile communication network. It is a figure which shows the procedure of the packet data transmission control in the base station controller by a prior art. It is a figure which shows the procedure of the control message transmission containing the size information of the buffer in the base station by a prior art. It is a figure which shows an example of the packet data transmission operation | movement between the base station controller by a prior art, and a base station. It is a figure which shows the other example of the packet data transmission operation | movement between the base station controller by a prior art, and a base station. It is a figure which shows the structure of the base station controller shown in FIG. 1 with which this invention is applied. It is a figure which shows the structure of the base station shown in FIG. 1 with which this invention is applied. It is a figure which shows the structure of the channel card shown in FIG. It is a figure which shows the user record in the base station by embodiment of this invention. It is a figure which shows the procedure of the packet data transmission control in the base station controller by embodiment of this invention. It is a figure which shows the procedure of the control message transmission containing the information regarding the number of transmission packets in the base station by embodiment of this invention. It is a figure which shows an example of the packet data transmission operation | movement between the base station controller and base station by embodiment of this invention. It is a figure which shows the other example of the packet data transmission operation | movement between the base station controller and base station by embodiment of this invention. It is a figure which shows the procedure of the packet data transmission control in the base station controller by other embodiment of this invention. (A) is a figure which shows the size of the base station buffer at the time of applying the packet data transmission operation | movement by a prior art, (B) is the base at the time of applying the packet data transmission operation | movement by embodiment of this invention. It is a figure which shows the size of a station buffer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Mobile terminal 20, 30 ... Base station 21 ... RF scheduler 210 ... Main controller 220 ... Line interface 230, 430 ... Switch (or router)
241, 243 ... Channel card 24-1 ... Input / output interface 24-2 ... Main processor 24-3 ... Memory 24-4 ... Modulator 24-5 ... Demodulator 250 ... High-frequency transceiver 40 ... Base station controller 410 ... Main controller 420 ... Line interface 440 ... Line interface 41 ... SDU / RLP processor 60 ... Gateway

Claims (10)

A base station controller for receiving packet data; and a mobile communication network including a base station having a buffer for receiving and storing packet data for transmission to a mobile terminal from the base station controller; In a method for controlling packet data transmission with the base station,
Reporting the number of packet data transmitted to the mobile terminal after being received from the base station controller by the base station to the base station controller;
Calculating the number of packet data transmitted from the base station controller to the base station but not yet transmitted from the base station to the mobile terminal based on the reported number of packet data When,
When packet data is received, the base station controller compares the size of the buffer with the number of untransmitted packet data;
Transmitting the received packet data from the base station controller to the base station when the size of the buffer is larger than the number of untransmitted packet data. The number of transmitted packet data The method of claim 1, wherein a is reported to the base station controller at a preset period by the base station. The number of transmitted packet data, when the base station transmits packet data to the mobile terminal, the method according to claim 1, characterized in that it is reported to the base station controller by the base station. The number of the received packet data to be transmitted to the base station The method of claim 1 wherein the the same as the difference between the number of packet data which is not the be transmitted and the size of the buffer. In an apparatus for controlling packet data transmission in a mobile communication network comprising a base station having a buffer for storing packet data for transmission to a mobile terminal,
Based on the number of packet data transmitted to the mobile terminal reported by the base station, it is transmitted from the base station controller to the base station, but not yet transmitted from the base station to the mobile terminal. A base station that calculates the number of packet data and transmits the received packet data to the base station when the size of the buffer of the base station is larger than the number of untransmitted packet data when the packet data is received A device comprising a controller. The base station controller reports the number of first packet data transmitted from the base station to the mobile terminal, which is reported by the base station at a preset period, from the base station controller to the base station. 6. The apparatus according to claim 5 , wherein the number of untransmitted packet data is calculated by subtracting from the number of transmitted second packet data. The base station controller determines the number of first packet data transmitted from the base station to the mobile terminal, which is reported by the base station after transmitting packet data to the mobile terminal, from the base station controller. 6. The apparatus of claim 5 , wherein the number of untransmitted packet data is calculated by subtracting from the number of second packet data transmitted to the base station. 6. The apparatus of claim 5 , wherein the number of received packet data transmitted to the base station is equal to a difference between a size of the buffer and the number of packet data not transmitted. A base station controller for receiving packet data, and a mobile communication network including a base station having a buffer for receiving and storing packet data for transmission to a mobile terminal from the base station controller, from the base station controller In a method for calculating the number of packet data transmitted to the base station,
The base station reports a first number indicating the number of packet data transmitted from the base station to the mobile terminal and a second number indicating the number of packet data stored in the buffer to the base station controller. Process,
If the first number and the second number are 0, the base station controller has transmitted to the base station at the previous reporting time, but has not yet been transmitted from the base station to the mobile terminal A third number indicating the number of packet data, and the number of packet data transmitted from the base station controller to the base station at the time of the current report but not transmitted from the base station to the mobile terminal. Checking whether the fourth numbers shown are the same;
And a step of setting the number of packet data transmitted from the base station controller to the base station to 0 when the third number and the fourth number are the same. The number of packet data transmitted from the base station controller to the base station is set to 0 when the third number and the fourth number are the same number of times set in advance. Item 10. The method according to Item 9 .

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